1. Field of the Invention
The present invention relates to a device and a method for identifying a human face.
2. Description of the Related Art
A conventional method for identifying a person (i.e. determining whose face is included) involves comparing registered information, such as feature values and performing a comparison between this information and a identification image. However, if conditions are not suitable for identification, that is, if a subject wears an article covering all or a part of the face such as sunglasses or a mask (hereinafter referred to as a “worn article”), or the lighting environment is too dark or too bright, or the subject faces sideways, the identification accuracy decreases.
In order to solve such a problem, it has been proposed that face identification devices corresponding to various face directions be prepared, that the face direction be detected in an identification image, and that a suitable face identification device be used (see to Pose Invariant Face Recognition, by F. J. Huang, Z. Zhou, H. Zhang, and T. Chen, Proceedings of the 4th IEEE International Conference on Automatic Face and Gesture Recognition, Grenoble, France, 2000, pp. 245-250.) Further, Laid-Open Japanese Patent Application No. 2000-215308 proposes providing an illumination sensor that senses the light intensity at the time of photography and also proposes that algorithms for extracting feature values and algorithms for identification are selected based on the light intensity previously determined. As such, for a plurality of functions relating to extraction of feature values and identification provided as mentioned above, image registration, algorithm tuning, studying of various parameters etc., must be performed for each of the functions.
Further Japanese Patent Publication No. 2923894, Laid-Open Japanese Patent Application No. 2002-015311 and 2003-132339 all discuss methods for maintaining identification accuracy in which an image or feature value determined when there are no unfavorable conditions is used to restore an image in which there are unfavorable conditions. However, with these methods, additional processing time is necessary and the accuracy of the restoration procedure is not guaranteed.